1. Field of the Invention
The present invention concerns a rotating anode for an x-ray tube of the type having an anode body composed of composite fiber material, mounted in a bearing system, that has a target surface with a focal ring and fibers with particularly high heat conductivity, with an axis-proximal cooling system associated with the anode body. The present invention also concerns a method producing such a rotating anode.
2. Description of the Prior Art
X-ray tubes with rotating anodes are known from Krestel, “Bildgebende Systeme für die medizinische Diagnostik”, pages 157f, in which the anode plate is composed of a molybdenum alloy. An x-ray-active cover layer made of a tungsten-rhenium alloy is applied to the base body. A graphite body is mounted under the anode plate for heat storage, dissipation and radiation, such that the anode plate is formed of a composite of Mo and C substrate, produced with solder technology, in which the heat spreads (radiates) corresponding to the heat conductivities and the heat storage properties. The WRe alloy of the cover layer can possess a thickness of 0.6 to 1.6 mm.
In x-ray tubes, one of the substantial technical challenges is the heat removal from the focal spot and the distribution of the heat of the focal spot to larger surfaces by rotation of the anode, which is exposed to high mechanical stresses from the rotation and from thermo-mechanical loads. Furthermore, in particular for application in computed tomography (CT), the usually heavy anode weight is a disadvantage since, due to the typical centrifugal forces resulting in CT from the device rotation, high stressing of the rotating anode bearing results from the heavy anode weight,
Therefore, in German patent application 102 29 069.5 a rotating anode with a basic body made of carbon fiber materials (CFC) is proposed in which fibers with particularly high heat conductivity effect an advantageous heat removal from the focal spot path of x-ray rotating anode tubes to an internally cooled bearing system.
A rotating anode for an x-ray tube, with an anode body composed of composite fiber material held mounted in a bearing system is known from U.S. Pat. No. 5,943,389 having a target surface with a focal ring and fibers with particularly high heat conductivity. An intermediate layer is applied to the anode body, on which a number of aligned carbon fibers are applied, on which in turn the focal ring is applied. The aligned carbon fibers serve to improve the heat removal from the focal ring into the anode body.
German OS 199 26 741 discloses a liquid-metal slide bearing with a cooling tube for a rotating anode, whereby the cooling medium flowing through the slide bearing absorbs and transports away the heat incidental in the operation of the x-ray tube, that arrives in the slide bearing from the anode.
In the abstract for JP 6 1022 546, a method is described to produce a rotating anode that is fashioned from formed components of composite fiber material, known as “prepregs.”
In such known x-ray rotating anodes, the problem of achieving good heat conductivity still exists.